The present invention relates to an information terminal device provided with a backlight, such as a mobile radio equipment.
Conventionally, an information terminal device such as a mobile radio equipment, as disclosed in, for example, JP-A-4-343539, includes a lighting means for illuminating an operational portion such as a number key, a function key or the like, and a number display, and further includes a lighting device for lighting the lighting means for a predetermined time by key operation. This lighting device includes a timer which is actuated for a predetermined time to light the lighting means every time the key is operated, and an optical sensor portion which detects light amount of the surroundings while the timer is actuated. Further, the lighting device includes an electric current control means which controls amount of driving electric current flowing in the lighting means according to the light receiving amount and which shuts off the driving electric current when the detected light amount of the surroundings exceeds the predetermined amount.
The conventional lighting device of the information terminal device such as the mobile radio equipment is constructed as described above. Therefore, when the key of the key operational portion is pushed down, the electric supply to the optical sensor portion is being performed together with the illumination light of the backlight for a predetermined time, so that more electric power of a battery is consumed than the device needs. Particularly, in a special mode requiring the large number of key operations, such as registration of telephone number, input of character message and the like, the electric power is still being supplied to the optical sensor portion, so that there is a problem that unnecessary electric power is consumed from the battery.
Further, it is necessary to separately provide a base plate for optical sensor in order to detect the surrounding light or to guide the surrounding light to an optical sensor on a common base plate by an optical guide, so that an extra space is required and cost-up is caused.
In order to solve the above problems, the invention has been made. An object of the invention is to provide a backlight control system of an information terminal device such as a mobile radio equipment, which does not consume the unnecessary electric power, and is superior in operational ability, visual recognizability and portability.
In order to achieve the above object, the information terminal device of the invention comprises a backlight means for illuminating a key operational portion or a LCD display portion, an optical sensor portion for detecting lightness of the surroundings, a backlight control means for lighting an illumination light according to the surrounding light for a predetermined time after the key operation, and an optical sensor control means which applies an electric current to the optical sensor portion at every regular intervals to detect the surrounding light. Except when the surrounding light is detected, application of the electric current to the optical sensor portion is forbidden.
Further, the information terminal device of the invention comprises a backlight means for illuminating a key operational portion or a LCD display portion, an optical sensor portion which is provided adjacently to a terminating LED and detects lightness of the surroundings, a backlight control means for adjusting the illumination light according to the surrounding light, an optical guide which guides the light of the terminating LED to the outside to perform terminating display at the terminating time and guides the surrounding light to the optical sensor at the illumination controlling time.
Further, the information terminal device of the invention comprises a key operational portion backlight means for illuminating a key operational portion, a LCD backlight means for illuminating a LCD display portion, a battery residual amount detecting means for detecting amount of the residual battery, and a backlight control means for adjusting the illumination light according to the battery residual amount.
Further, the information terminal device of the invention comprises a key operational portion backlight means for illuminating a key operational portion, a LCD backlight means for illuminating a LCD display portion, an optical sensor portion for detecting lightness of the surroundings, and a backlight control means for adjusting the illumination light according to the surrounding light. The backlight control means switches, according to the surrounding light when the key operation is performed, control for lighting both the key operational portion backlight means and the LCD backlight means, control for lighting only the LD backlight means, and control for not lighting all backlight means.